Wireless power supply systems have been proposed that supply electric power to electrical loads mounted on vehicles via a wireless connection between power transmission devices provided on the ground side and power receiving devices provided on the vehicle side. A vehicle using such a wireless power supply system and parked in a power supply position may be moved from the power supply position during power supply. The system is required to immediately detect a positional shift between a power transmission coil and a power receiving coil due to the movement of the vehicle so as to stop the power supply.
For example, International Publication WO 2013/046391 discloses a system in which a power transmission device and a power receiving device communicate with each other so as to control an appropriate supply of voltage. International Publication WO 2013/046391 discloses that the communication between the power transmission device and the power receiving device is implemented for a second cycle, and the power transmission device is controlled so as to appropriately transmit electric power for a first cycle shorter than the second cycle.
International Publication WO 2013/046391 fails to disclose that the power transmission is regulated when the positions of the power transmission coil and the power receiving coil are shifted from each other during wireless power supply.